Among conventional D/A converters that use the R-2R system is a D/A converter disclosed, for example, in Japanese Patent Laid-Open No. 324139/1993. This D/A converter comprises a plurality of functional sections accommodated in MCU and performs various functions and operations. It has a register section for stopping the supply of a power into each of the plurality of functional sections including the CPU, and a switch is used to stop the supply of current into an internal circuit.
According to the conventional D/A converter, addition of a switch serves to suppress the current consumption during the unused condition of the D/A converter. However, a variation in impedance of the reference voltage disadvantageously results in a variation in the current value fed. To address this problem generally requires the use of an exterior type current feed buffer for use during operation of the D/A converter.